Test signal generating apparatus for communications equipment and test signal generating method for communications equipment

Abstract

A test signal generating apparatus for communications equipment sequentially uses first and second sequence information which are stored in a sequence memory for storing the first sequence information including a reading order and read addresses of unit data including I and Q waveform data, and desired signal levels to be set to the unit data, and the second sequence information including frequency offsets. Consequently, the test signal generating apparatus provides frequency offsets at a plurality of steps every predetermined frequency intervals by using a predetermined carrier frequency as a reference, with respect to the I and Q waveform data at a digital stage up to digital-to-analog converters, and outputs a test signal in the frequency hopping system.

1. A test signal generating apparatus for communications equipment, comprising:
 a pair of waveform memories in which I component waveform digital data (hereinafter, referred to as I waveform data) and Q component waveform digital data (hereinafter, referred to as Q waveform data) which configure a set of digital baseband quadrature signals I and Q in at least one or more types of unit data serving as sources of a test signal to be finally output, are respectively stored in advance at predetermined addresses; 
 a read control unit to sequentially output the I waveform data and the Q waveform data from the pair of waveform memories; 
 a pair of multipliers to set signal levels of the I waveform data and the Q waveform data which are sequentially output from the pair of waveform memories to desired signal levels, respectively; 
 a pair of digital-to-analog converters which convert the I waveform data and the Q waveform data which are sequentially output from the pair of multipliers into an I waveform analog signal and a Q waveform analog signal, respectively; 
 a frequency offset unit which sets offset frequencies for providing frequency offsets at a plurality of steps at predetermined intervals by using a predetermined carrier frequency provided to the test signal as a reference, with respect to the I waveform data and the Q waveform data between the pair of waveform memories and the pair of digital-to-analog converters; 
 a sequence memory which stores in advance: (i) first sequence information including a reading order and read addresses of the unit data including the I waveform data and the Q waveform data stored in the pair of waveform memories, and the desired signal levels to be set in the unit data including the I waveform data and the Q waveform data read from the pair of waveform memories; and (ii) second sequence information including the offset frequencies set for providing frequency offsets at a plurality of steps at predetermined intervals by using the predetermined carrier frequency provided to the test signal as a reference, with respect to the unit data including the I waveform data and the Q waveform data read from the pair of waveform memories; 
 a sequence control unit which (i) reads the first sequence information from the sequence memory, instructs the read control unit about the reading order and the read addresses included in the first sequence information, thereby causing the read control unit to sequentially output the I waveform data and the Q waveform data from the pair of waveform memories, and instructs the pair of multipliers about the desired signal levels included in the first sequence information in response to a timing at which the I waveform data and the Q waveform data are output from the pair of waveform memories, thereby causing the pair of multipliers to set signal levels of the I waveform data and the Q waveform data which are sequentially output from the pair of waveform memories respectively to the desired signal levels; and (ii) reads the second sequence information from the sequence memory, and instructs the frequency offset unit about the offset frequencies included in the second sequence information, thereby causing the frequency offset unit to set the offset frequencies for providing frequency offsets at a plurality of steps at predetermined intervals by using the predetermined carrier frequency provided to the test signal as a reference, with respect to the unit data including the I waveform data and the Q waveform data; and 
 a test signal output unit which converts the I waveform analog signal and the Q waveform analog signal which are sequentially output from the pair of digital-to-analog converters into a high-frequency signal by using a carrier frequency signal after carrying out quadrature modulation to the signals, thereby causing the high-frequency signal to be output finally in the form of the modulating signal and as a test signal along with frequency offsets at a plurality of steps at predetermined intervals by using the predetermined frequency as a reference. 
 
     
     
       2. The test signal generating apparatus for communications equipment according to  claim 1 , wherein the frequency offset unit is provided between the pair of waveform memories and the pair of multipliers. 
     
     
       3. The test signal generating apparatus for communications equipment according to  claim 1 , wherein the frequency offset unit is provided between the pair of multipliers and the pair of digital-to-analog converters. 
     
     
       4. The test signal generating apparatus for communications equipment according to  claim 1 , wherein the test signal output unit comprises:
 a quadrature modulator which quadrature-modulates the I waveform analog signal and the Q waveform analog signal which are sequentially output from the pair of digital-to-analog converters by using a local oscillation signal from a local oscillator, to output a modulating signal; 
 a frequency converter which converts the modulating signal output from the quadrature modulator into a high-frequency signal by using a carrier frequency signal from an oscillator, to output a signal in the form of the modulating signal and as a test signal along with a predetermined carrier frequency; and a band-pass filter which eliminates unnecessary frequency components included in the test signal output from the frequency converter, thereby causing the test signal to be output finally in the form of the modulating signal and as a test signal along with offset frequencies at a plurality of steps at predetermined intervals by using the predetermined carrier frequency as a reference. 
 
     
     
       5. The test signal generating apparatus for communications equipment according to  claim 4 , wherein:
 when at least the band-pass filter is provided as a component having an uneven frequency characteristic to the test signal output unit, 
 the sequence memory stores in advance third sequence information including level offset values for setting level offset values from a signal level at the predetermined carrier frequency serving as the reference to be greater, as there becomes greater an absolute value of offset frequencies for providing frequency offsets at a plurality of steps at predetermined intervals by using as a reference the predetermined carrier frequency provided to the test signal as the offset frequencies included in the second sequence information, and 
 the sequence control unit reads the third sequence information from the sequence memory, and instructs the pair of multipliers about the level offset values included in the third sequence information in response to a timing at which the I waveform data and the Q waveform data are output from the pair of waveform memories, thereby causing the multipliers to set level offset values from a signal level at the predetermined carrier frequency serving as the reference to be greater, as there becomes greater an absolute value of offset frequencies for providing frequency offsets at a plurality of steps at predetermined intervals by using as a reference the predetermined carrier frequency provided to the test signal as the offset frequency information included in the second sequence information. 
 
     
     
       6. The test signal generating apparatus for communications equipment according to  claim 1 , wherein:
 the sequence memory stores in advance fourth sequence information including a number of repetitions of reading I waveform data and Q waveform data for each of the unit data from the pair of waveform memories in order to set a number of repetitions for each of the unit data included in the test signal to be finally output, and 
 the sequence control unit reads the fourth sequence information from the sequence memory, and instructs the read control unit about the number of repetitions of reading I waveform data and Q waveform data for each of the unit data included in the fourth sequence information from the pair of waveform memories in response to a timing at which the I waveform data and the Q waveform data are output from the pair of waveform memories, thereby causing the read control unit to sequentially output from the pair of waveform memories the unit data continuously the number of times corresponding to the number of repetitions of reading I waveform data and Q waveform data for each of the unit data from the pair of waveform memories. 
 
     
     
       7. The test signal generating apparatus for communications equipment according to  claim 1 , wherein the second sequence information including offset frequencies to be stored in the sequence memory is set as offset frequencies which enable achievement of frequency hopping which enables achieving a carrier frequency of a test signal imitating a Global System for Mobile Communication (GSM) signal as the test signal is made to vary with time, whereby it is possible to achieve an interfering wave resistance test for a device to be tested in a Wideband Code Division Multiple Access (WCDMA) system by means of the GSM signal in such a manner that the GSM signal discretely moves within a range of received frequencies of the device to be tested in the WCDMA system. 
     
     
       8. The test signal generating apparatus for communications equipment according to  claim 1 , wherein the pair of multipliers multiply the I waveform data and the Q waveform data output from the pair of waveform memories by a gain multiplication value determined based on the signal levels instructed by the sequence control unit, thereby setting signal levels of the I waveform data and the Q waveform data output from the pair of waveform memories to the signal levels included in the first sequence information which is stored in the sequence memory. 
     
     
       9. The test signal generating apparatus for communications equipment according to  claim 5 , wherein the pair of multipliers multiply the I waveform data and the Q waveform data output from the pair of waveform memories by a gain multiplication value determined based on the level offset values included in the third sequence information, the level offset values being instructed by the sequence control unit, thereby setting signal levels of the I waveform data and the Q waveform data read from the pair of waveform memories to the level offset values included in the third sequence information which is stored in the sequence memory. 
     
     
       10. The test signal generating apparatus for communications equipment according to  claim 1 , further comprising:
 a test database formed in a hard disk drive having provided therein a waveform database which stores I waveform data and Q waveform data of the unit data included in the test signal and a sequence database which stores various sequence information; and 
 a data writing unit connected to the test database, 
 wherein:
 the I waveform digital data and the Q waveform digital data stored in the waveform database, and the various sequence information stored in the sequence database are prepared outside, and downloaded into the test database, and 
 I waveform digital data and Q waveform digital data corresponding to a test signal to be newly output are read from the waveform database via the data writing unit and written into the pair of waveform memories, and at the same time, sequence information corresponding to the test signal to be newly output is read from the sequence database and written into the sequence memory. 
 
 
     
     
       11. The test signal generating apparatus for communications equipment according to  claim 1 , further comprising:
 a numerical control oscillator which causes the sequence control unit to specify, as the offset frequencies included in the second sequence information read from the sequence memory, offset frequencies (ω′) for providing frequency offsets at a plurality of steps at predetermined intervals by using the predetermined carrier frequency provided to the test signal as a reference, 
 wherein:
 the numerical control oscillator generates a sine wave sin ω′ (t) and a cosine wave cos ω′ (t) which correspond to the offset frequencies (ω′) specified by the sequence control unit, and transmits the sine wave sin ω′ (t) and the cosine wave cos ω′ (t) to the frequency offset unit, and 
 when frequencies ω (=2Πf) of the I waveform data and the Q waveform data are offset by offset frequencies ω′ (=2Πf′) stored in the sequence memory, the frequency offset unit carries out frequency offset processing in such a manner that, when the I waveform data and the Q waveform data are respectively denoted by:
   cos ω(t), sin ω(t), 
 
 
 
       the sine wave and cosine wave are converted respectively into:
   cos {ω(t)+ω′(t)}, sin {ω(t)+ω′(t)}. 
 
     
     
       12. The test signal generating apparatus for communications equipment according to  claim 11 , wherein the frequency offset unit converts the I waveform data cos ω (t) and the Q waveform data sin ω (t) respectively into cos {ω (t)+ω′ (t)}, sin {ω (t)+ω′ (t)} using the relationships:
   cos {ω(t)+ω′(t)}=−sin ω( t )·sin ω′( t )+cos ω( t )·cos ω′( t ), and 
   sin {ω(t)+ω′(t)}=cos ω( t )·sin ω′( t )+sin ω( t )·cos ω′( t ) . 
 
     
     
       13. The test signal generating apparatus for communications equipment according to  claim 12 , wherein the frequency offset unit comprises:
 first and second multipliers which multiply the I waveform data cos ω(t) and the Q waveform data sin ω(t) respectively by a first frequency offset component cos ω′ (t); 
 third and fourth multipliers which multiply the I waveform data cos ω (t) and the Q waveform data sin ω (t) respectively by a second frequency offset component sin ω′ (t); 
 a first adder which outputs the first frequency offset cos {ω(t)+ω′ (t) }=−sin ω(t) ∩sin ω′ (t) +cos ω′ (t) ·cos ω′ (t) by adding an output from the first multiplier and an output from the fourth multiplier; and 
 a second adder which outputs the second frequency offset sin {ω(t)+ω′ (t) }=−cos ω(t) ∩sin ω′ (t) +sin ω′ (t) ·cos ω′ (t) by adding an output from the second multiplier and an output from the third multiplier. 
 
     
     
       14. A test signal generating method for communications equipment, comprising:
 respectively storing in advance I component waveform digital data (hereinafter, referred to as I waveform data) and Q component waveform digital data (hereinafter, referred to as Q waveform data) which configure a set of digital baseband quadrature signals I and Q in at least one or more types of unit data serving as sources of a test signal to be finally output, at predetermined addresses of a pair of waveform memories; 
 causing a sequence memory to store in advance (i) first sequence information including a reading order and read addresses of the unit data including the I waveform data and the Q waveform data stored in the pair of waveform memories, and desired signal levels to be set in the unit data including the I waveform data and the Q waveform data read from the pair of waveform memories, and (ii) second sequence information including offset frequencies which are set for providing frequency offsets at a plurality of steps at predetermined intervals by using a predetermined carrier frequency provided to the test signal as a reference, with respect to the unit data including the I waveform data and the Q waveform data read from the pair of waveform memories; 
 causing a sequence control unit to read the first sequence information from the sequence memory, and instruct a read control unit about the reading order and the read addresses included in the first sequence information to sequentially output the I waveform data and the Q waveform data from the pair of waveform memories; 
 causing the sequence control unit to read the first sequence information from the sequence memory, and instruct a pair of multipliers about the desired signal levels included in the first sequence information in response to a timing at which the I waveform data and the Q waveform data are output from the pair of waveform memories, thereby respectively setting signal levels of the I waveform data and the Q waveform data which are sequentially output from the pair of waveform memories to the desired signal levels; 
 causing a pair of digital-to-analog converters to respectively convert the I waveform data and the Q waveform data which are sequentially output from the pair of multipliers into an I waveform analog signal and a Q waveform analog signal; 
 at a digital stage from the pair of waveform memories up to the pair of digital-to-analog converters, causing the sequence control unit to read the second sequence information from the sequence memory, and instruct a frequency offset unit about the offset frequencies included in the second sequence information to set the offset frequencies for providing frequency offsets at a plurality of steps at predetermined intervals by using the predetermined carrier frequency provided to the test signal as a reference, with respect to the unit data including the I waveform data and the Q waveform data; and 
 causing a test signal output unit to convert the I waveform analog signal and the Q waveform analog signal which are sequentially output from the pair of digital-to-analog converters into a high-frequency signal by using a carrier frequency signal after carrying out quadrature-modulation to the signals, to output a signal finally in the form of the modulating signal and as a test signal along with frequency offsets at a plurality of steps at predetermined intervals by using the predetermined carrier frequency as a reference. 
 
     
     
       15. The test signal generating method for communications equipment according to  claim 14 , wherein setting the frequency offsets is carried out in a frequency offset unit provided between the pair of waveform memories and the pair of multipliers. 
     
     
       16. The test signal generating method for communications equipment according to  claim 14 , wherein setting the offset frequency information is carried out in a frequency offset unit provided between the pair of multipliers and the pair of digital-to-analog converters. 
     
     
       17. The test signal generating method for communications equipment according to  claim 14 , wherein outputting the I waveform analog signal and the Q waveform analog signal finally in form of the modulating signal and as a test signal along with frequency offsets at a plurality of steps at predetermined intervals by using the predetermined frequency as a reference comprises:
 causing a quadrature modulator to output the I waveform analog signal and the Q waveform analog signal which are sequentially output from the pair of digital-to-analog converters, as a modulating signal quadrature-modulated by using a local oscillation signal from a local oscillator; 
 causing a frequency converter to convert the modulating signal output from the quadrature modulator into a high-frequency signal by using a carrier frequency signal from an oscillator, to output a signal in the form of the modulating signal and as a test signal along with the predetermined carrier frequency; and 
 causing a band-pass filter to eliminate unnecessary frequency components included in a test signal output from the frequency converter, to output a signal finally in the form of the modulating signal and as a test signal along with frequency offsets at a plurality of steps at predetermined intervals by using the predetermined carrier frequency as a reference. 
 
     
     
       18. The test signal generating method for communications equipment according to  claim 17 , further comprising:
 when at least the band-pass filter is provided as a component having an uneven frequency characteristic to the test signal output unit, 
 causing the sequence memory to store in advance third sequence information which includes level offset values for setting level offset values from a signal level at the predetermined carrier frequency serving as the reference to be greater, as there becomes greater an absolute value of offset frequencies for providing frequency offsets at a plurality of steps at predetermined intervals by using as a reference the predetermined carrier frequency provided to the test signal as the offset frequencies included in the second sequence information; and 
 causing the sequence control unit to read the third sequence information from the sequence memory, and instruct the pair of multipliers about the level offset values included in the third sequence information in response to a timing at which the I waveform data and the Q waveform data are output from the pair of waveform memories, thereby setting level offset values from a signal level at the predetermined carrier frequency serving as the reference to be greater, as there becomes greater an absolute value of offset frequencies for providing frequency offsets at a plurality of steps at predetermined intervals by using as a reference the predetermined carrier frequency provided to the test signal as the offset frequencies included in the second sequence information. 
 
     
     
       19. The test signal generating method for communications equipment according to  claim 14 , further comprising:
 causing the sequence memory to store in advance fourth sequence information including a number of repetitions of reading I waveform data and Q waveform data for each of the unit data from the pair of waveform memories in order to set a number of repetitions for each of the unit data included in the test signal to be finally output; and 
 causing the sequence control unit to read the fourth sequence information from the sequence memory, and instruct the read control unit about the number of repetitions of reading I waveform data and Q waveform data for each of the unit data included in the fourth sequence information from the pair of waveform memories in response to a timing at which the I waveform data and the Q waveform data are output from the pair of waveform memories, thereby sequentially outputting from the pair of waveform memories the unit data continuously the number of times corresponding to the number of repetitions of reading I waveform data and Q waveform data for each of the unit data from the pair of waveform memories. 
 
     
     
       20. The test signal generating method for communications equipment according to  claim 14 , wherein, in causing the sequence memory to store in advance the second sequence information including the offset frequencies, the second sequence information including the offset frequencies to be stored in the sequence memory is set as offset frequencies which enable achievement of frequency hopping which enables achieving a carrier frequency of a test signal imitating a Global System for Mobile Communication (GSM) signal as the test signal is made to vary with time, whereby it is possible to achieve an interfering wave resistance test for a device to be tested in a Wideband Code Division Multiple Access (WCDMA) system by the GSM signal in such a manner that the GSM signal discretely moves within a range of received frequencies of the device to be tested in the WCDMA system. 
     
     
       21. The test signal generating method for communications equipment according to  claim 14 , wherein setting signal levels of the I waveform data and the Q waveform data which are sequentially output from the pair of waveform memories to desired signal levels respectively comprises using the pair of multipliers to multiply the I waveform data and the Q waveform data output from the pair of waveform memories by a gain multiplication value determined based on the signal levels instructed by the sequence control unit, whereby signal levels of the I waveform data and the Q waveform data read from the pair of waveform memories are set to the signal levels included in the first sequence information stored in the sequence memory. 
     
     
       22. The test signal generating method for communications equipment according to  claim 18 , wherein setting signal levels of the I waveform data and the Q waveform data which are sequentially output from the pair of waveform memories to desired signal levels respectively comprises using the pair of multipliers to multiply the I waveform data and the Q waveform data output from the pair of waveform memories by a gain multiplication value determined based on the level offset values included in the third sequence information, which are instructed by the sequence control unit, whereby signal levels of the I waveform data and the Q waveform data read from the pair of waveform memories are set to the level offset values included in the third sequence information stored in the sequence memory. 
     
     
       23. The test signal generating method for communications equipment according to  claim 14 , further comprising:
 preparing: a test database formed in a hard disk drive having provided therein a waveform database which stores the I waveform data and the Q waveform data of the unit data included in the test signal and a sequence database which stores various sequence information; and a data writing unit connected to the test database; 
 downloading into the test database the I waveform data and the Q waveform data which are prepared outside to be stored in the waveform database, and the various sequence information stored in the sequence database; and 
 causing the data writing unit to read from the waveform database the I waveform data and the Q waveform data corresponding to a test signal to be newly output to be written into the pair of waveform memories, and to read sequence information corresponding to the test signal to be newly output from the sequence database to be written into the sequence memory. 
 
     
     
       24. The test signal generating method for communications equipment according to  claim 14 , wherein setting the offset frequencies comprises:
 causing a numerical control oscillator to specify offset frequencies (ω′) for providing frequency offsets at a plurality of steps at predetermined intervals by using as a reference the predetermined carrier frequency of the test signal, as the offset frequencies included in the second sequence information read from the sequence memory; 
 causing the numerical control oscillator to generate a sine wave sin ω′ (t) and a cosine wave cos ω (t), which correspond to the offset frequencies (ω′) specified by the sequence control unit, to be transmitted to the frequency offset unit; and 
 when frequencies ω (=2Πf) of the I waveform data and the Q waveform data are offset by offset frequencies ω′ (=2Πf′) stored in the sequence memory, causing the frequency offset unit to carry out frequency offset processing in such a manner that, when the I waveform data and the Q waveform data are respectively denoted by:
   cos ω(t), sin ω(t), 
 
  the sine wave and cosine wave are converted respectively into:
   cos {ω(t)=ω′(t)}, sin {ω(t)+ω′(t)}. 
 
 
     
     
       25. The test signal generating method for communications equipment according to  claim 24 , wherein the frequency offset unit converts the I waveform data cos ω (t) and the Q waveform data sin ω (t) respectively into cos {ω (t)+ω′ (t)}, sin {ω (t)+ω′ (t)} using the relationships:
   cos {ω(t)+ω′(t)}=−sin ω( t )·sin ω′( t )+cos ω( t )·cos ω′( t ), and 
   sin {ω(t)+ω′(t)}=cos ω( t )·sin ω′( t )+sin ω( t )·cos ω′( t ). 
 
     
     
       26. The test signal generating method for communications equipment according to  claim 25 , causing the frequency offset unit to carry out frequency offset processing comprises:
 causing first and second multipliers to multiply the I waveform data cos ω (t) and the Q waveform data sin ω (t) respectively by a first frequency offset component cos ω′ (t); 
 causing third and fourth multipliers to multiply the I waveform data cos ω (t) and the Q waveform data sin ω (t) by a second frequency offset component sin ω (t); 
 causing a first adder to add an output from the first multiplier and an output from the fourth multiplier, thereby outputting the first frequency offset cos {ω (t)+ω′ (t)}=−sin ω (t)·sin ω′ (t)+cos ω (t)·cos ω′ (t) ; and 
 causing a second adder to add an output from the second multiplier and an output from the third multiplier, thereby outputting the second frequency offset sin {ω (t)+ω′ (t)}=−cos ω (t)·sin ω′ (t)+sin ω (t)·cos ω′ (t).